修改Springboot 响应过程，包装返回值 |
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修改Springboot 响应过程，包装返回值
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问题
前端一直不太认同http status(状态码)表达操作成功与否的方式，强烈要求所有接口都返回200，在响应体中增加code来表示操作是否成功。
比如当使用POST方式请求接口/api/user/2 时 当没有操作权限时两种响应 请求接口: /api/user/2 请求方法: POST 请求体：......(json格式的参数) 原响应格式: http status: 403 响应体: { msg: '没有操作权限' } 复制代码前端想要的响应格式： http status: 200 响应体: { code: 403, msg: '没有操作权限' } 复制代码 办法 1. 修改每个接口的返回值最简单粗暴的方式：定义一个类如下： @Data public class Res{ private Integer code; private String msg; private Object content; } 复制代码将每个service的返回值都set给content，set相应的code和msg，然后controller将该对象返回给前端。 也可以每个接口都返回JSONObject的实例json @GetMapping("/{id}") public JSONObject getOne((@PathVariable Integer id){ Person person = personService.findById(id); JSONObject json = new JSONObject(); json.put("code", 200); json.put("msg", "成功"); json.put("content", person); return json; } 复制代码功能完成，但是看到满屏的Res或者JSONObject操作，这么多重复代码，实在不应该。 2. 改进，修改SpringBoot原有流程SpringBoot的请求处理过程如下：
在第二张图中可以看到HandlerMethodReturnValueHandler在处理所有响应的内容，只要干预他的处理过程就能将原有数据包装起来 下面是该类的源码 public interface HandlerMethodReturnValueHandler { /** * Whether the given {@linkplain MethodParameter method return type} is * supported by this handler. * @param returnType the method return type to check * @return {@code true} if this handler supports the supplied return type; * {@code false} otherwise */ boolean supportsReturnType(MethodParameter returnType); /** * Handle the given return value by adding attributes to the model and * setting a view or setting the * {@link ModelAndViewContainer#setRequestHandled} flag to {@code true} * to indicate the response has been handled directly. * @param returnValue the value returned from the handler method * @param returnType the type of the return value. This type must have * previously been passed to {@link #supportsReturnType} which must * have returned {@code true}. * @param mavContainer the ModelAndViewContainer for the current request * @param webRequest the current request * @throws Exception if the return value handling results in an error */ void handleReturnValue(@Nullable Object returnValue, MethodParameter returnType, ModelAndViewContainer mavContainer, NativeWebRequest webRequest) throws Exception; } 复制代码实现该类的两个方法就能自定义处理过程。 首先还是要定义一个工具类： public class Res { // protected final static Res OK = new Res( HttpStatus.OK.value(),"成功",""); private Integer code; private String msg; private String message; /** * 返回正常信息时，将数据放入该字段 */ private Object content; /** * 成功响应并需要返回数据时，使用该构造方法 * @param data */ protected Res(Object data) { this.code = 200; this.msg = "成功"; this.message = "success"; this.content = data; } Res(Integer code,String msg, String message){ this.msg = msg; this.code = code; this.message = message; } public Integer getCode() { return code; } public String getMsg() { return msg; } public String getMessage() { return message; } public Object getContent() { return content; } } 复制代码 然后实现 HandlerMethodReturnValueHandler public class WrapReturnValueHandler implements HandlerMethodReturnValueHandler { private Res ok = new Res(null); private RequestResponseBodyMethodProcessor target; public WrapReturnValueHandler(RequestResponseBodyMethodProcessor target) { this.target = target; } @Override public boolean supportsReturnType(MethodParameter methodParameter) { return true; } @Override public void handleReturnValue(Object o, MethodParameter methodParameter, ModelAndViewContainer modelAndViewContainer, NativeWebRequest nativeWebRequest) throws Exception { Executable executable = methodParameter.getExecutable(); Method method = (Method) executable; Class returnType = method.getReturnType(); if (returnType.equals(Void.class)) { target.handleReturnValue(ok, methodParameter, modelAndViewContainer, nativeWebRequest); } else if ( returnType.equals( Res.class )) { target.handleReturnValue(o, methodParameter, modelAndViewContainer, nativeWebRequest); else { target.handleReturnValue(new Res(o), methodParameter, modelAndViewContainer, nativeWebRequest); } } } 复制代码 最后将这个实现类加入到SpringBoot流程中 @Configuration public class InitializingAdvice implements InitializingBean { private final static Logger log = LoggerFactory.getLogger( InitializingAdvice.class ); @Resource private RequestMappingHandlerAdapter adapter; @Override public void afterPropertiesSet() { List returnValueHandlers = adapter.getReturnValueHandlers(); List handlers = new ArrayList(returnValueHandlers); this.decorateHandlers(handlers); adapter.setReturnValueHandlers(handlers); } private void decorateHandlers(List handlers) { for (HandlerMethodReturnValueHandler handler : handlers) { if (handler instanceof RequestResponseBodyMethodProcessor) { WrapReturnValueHandler decorator = new WrapReturnValueHandler( (RequestResponseBodyMethodProcessor) handler); int index = handlers.indexOf(handler); handlers.set(index, decorator); break; } } } } 复制代码这样所有的响应在转化为流之前就能将内容包装成预期格式 当然抛出异常可以使用注解@ControllerAdvice捕获控制，以控制http status，然后主动将响应构造成Res实例 |
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